Automobile safety regulations in the United States and globally have increased and remain an important concern for automobile manufacturers. In 1984, the U.S. government required all cars produced after Apr. 1, 1989 to have driver's side airbags. Dual front airbags were required in automobiles in 1998. Airbags consist of a flexible and inflatable envelope. Airbags are commonly used for cushioning against hard interior objects, such as steering wheels, in the event of a crash.
In a vehicle equipped with an air bag system, the airbag is instantly inflated in the event of a collision to protect the occupant from injury. The airbag is typically inflated by pressurized gas from an inflating tube mounted within the vehicle. Typically, airbag systems are designed to inflate the airbag within 20 to 40 milliseconds after the initial impact. The pressurized gas supplied to inflate the airbag within such a short period of time produces forces tending to pull and separate the airbag from the inflating tube. If the airbag is separated from the inflating tube, the airbag may not inflate or only partially inflate and, as a result, fail to adequately prevent the occupant's impact with hard interior objects of the vehicle, such as a steering wheel, door or the like.
To resist these forces, a clamping device of considerable strength must be provided to insure safety of the occupant. Ring clamps are typically used to secure the airbag to the inflating tube. These ring clamps are positioned around the inflating tube and the airbag to clamp the airbag to the inflating tube. However, these ring clamps are problematic for a number of reasons. First, during inflation of the airbag, these ring clamps tend to slip off of the inflating tube. Others have attempted to cure this problem by attaching a hook-like device to the inflating tube to prevent the ring clamp from sliding off of the inflating tube. However, this solution is costly and is only a preventive measure rather than curing the deficiencies of the clamps.
Second, these ring clamps are locked in a closed position by crimping or otherwise locking the ring clamp. However, the crimping or locking occurs in the same direction of the load path. In other words, the ring clamp is locked in the same direction as the applied force, which is typically a direction parallel to the clamp's circumference. As a result, the residual clamp load of these clamps is miniscule in view of the initial compression load applied to these ring clamps.
FIG. 12 illustrates a prior art clamp tested by applying different initial clamp loads and determining the residual load. As shown in FIG. 12, the residual clamp load is about 5% of the initial compression load. Therefore, these ring clamps are unreliable in maintaining connection of the airbag to the inflating tube, especially if the occupant contacts the airbag with a high amount of force.
As a result of the relatively low residual clamp load, manufacturers are forced to use expensive metal materials, such as high grade stainless steel. Mild steels, which typically cost less, were thought to be incapable of adequately resisting the forces caused by the nearly instantaneous inflation of the airbag. Therefore, these prior art ring clamps were relatively costly to manufacture.
The installation of these ring clamps is also deficient. The compression load used in installing these clamps varies widely and cannot be consistently applied. In addition, automobile manufacturers are unable to effectively record and track the installation of the clamps.
Therefore, a need exists for an improved clamp and method for installing clamps onto airbag inflating devices. While discussed in terms of use of clamps on airbag inflating devices, this is for illustration purpose only, and this invention should not be deemed as limited to the field of air bag systems. The clamps and methods for installing the clamps are applicable to many other fields as will be appreciated by a person of ordinary skill in the art.